The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
The present invention relates to marine and naval engineering and architecture as pertains to shapes and configurations of ships, boats and other water vessels, more particularly to hull forms of such vessels.
The term xe2x80x9ctumblehomexe2x80x9d (alternatively spelled xe2x80x9ctumble homexe2x80x9d or xe2x80x9ctumble-homexe2x80x9d) refers to a property of a water vessel""s hull wherein its topside, or some portion thereof, is inclined inward. Generally according to conventional tumblehome-type monohull designs, the two sides of the vessel are sloped, above the maximum beam (widest width or breadth), toward the middle or center of the vessel. These known monohull tumblehome hull designs typically are beset with certain undesirable characteristics. They have a poor righting arm, since the tumblehome feature decreases the water plane area as the ship heels (tilts to one side; lists). They have poor damage stability, because the above-water volume is limited by the tumblehome feature. They have restricted useable superstructure volume and width at the deck level. They are characterized by unusual sea-keeping responsiveness along with ongoing concern regarding the dynamic stability in a seafaring way; this is probably attributable to the broad transom (which has large above-water volume associated therewith) in combination with the wave-piercing bow (which has limited above-water volume associated therewith).
To some extent, trimarans are intended to reduce or eliminate the stability problems associated with conventional monohull tumblehome designs. A trimaran configuration includes three separate hulls, usually a main hull and two much smaller, pontoon-like or float-like hulls (sometimes called xe2x80x9coutriggersxe2x80x9d) on each side. A main drawback of a typical trimaran design relates to the fact that the large separation distance between the main hull and the outer hull amplifies the bending moment. Hence, each cross-structure connecting the main hull to an outer hull (outrigger) must be strong enough to handle the large bending moments caused by hydrodynamic loads. Consequently, the cross-structures represent significant increases in structural weight.
In view of the foregoing, it is an object of the present invention to provide a tumblehome-type hullform which is more stable than conventional tumblehome-type hull forms.
It is a further object of the present invention to provide a tumblehome-type hullform which is characterized by greater internal volume than is typical conventional tumblehome-type hull forms.
It is another object of the present invention to provide a tumblehome-type hullform which has better sea-keeping characteristics than is typical of tumblehome-type hull forms.
It is a further object of the present invention to provide a tumblehome-type hullform which is more stable than conventional tumblehome-type hullforms, but which is lighter than conventional trimaran hullforms.
Typically according to the present invention, a water vehicle such as a water transportation vehicle has a length, an imaginary lengthwise axis, a port side and a starboard side. The vehicle is about equivalently configured on each of its sides. The vehicle comprises a tumblehome outer surface, an inner surface and a junctional surface. The inner surface generally is located more proximate the lengthwise axis than the tumblehome outer surface. The junctional surface joins each of the tumblehome outer surface and the inner surface so as to generally be interposed between the tumblehome outer surface and the inner surface.
In accordance with many embodiments of the present invention, a hull comprises a back- section and a front section. The hull is characterized by a length and by an imaginary horizontal plane passing therethrough. The back section includes a pair of lateral fins and a medial portion between the lateral fins. The medial portion includes a pair of medial faces. Each fin includes a lateral tumblehome face and a crosswise face. Each crosswise face at least substantially is sloped at a smaller angle with respect to the imaginary horizontal plane than are the medial faces and the lateral tumblehome faces. Each crosswise face and a lateral tumblehome face form an at least substantially horizontal fin edge. Each crosswise face and a medial face form an at least substantially horizontal junctional corner. Each crosswise face at least substantially is sloped at an angle with respect to the imaginary horizontal plane which, to at least a substantial degree, gradually increases in accordance with the forward lengthwise direction of the hull.
In accordance with the present invention, the medial faces can be sloped in a tumblehome or conventional (nontumblehome) fashion. According to some of the embodiments wherein the medial faces are sloped in tumblehome fashion, the medial tumblehome faces and the lateral tumblehome faces at least substantially are sloped at at least substantially the same at least substantially constant angle with respect to the imaginary horizontal plane.
A typical hull configuration according to this invention has an imaginary centerline and comprises a stern surface, an outer starboard tumblehome surface, an inner starboard surface, an outer port tumblehome surface, an inner port surface, a starboard obliquely downfacing surface and a port obliquely downfacing surface. The outer starboard tumblehome surface, the inner starboard surface, the outer port tumblehome surface, the inner port surface, the starboard obliquely downfacing surface and the port obliquely downfacing surface each extend from the stern surface in a generally forward direction. The starboard obliquely downfacing surface connects the outer starboard tumblehome surface and the inner starboard surface. The port obliquely downfacing surface connects the outer port tumblehome surface and the inner port surface. The outer starboard tumblehome surface and the outer port tumblehome surface are each approximately parallel to the centerline. Proceeding from the stern surface in a generally forward direction, the inner starboard surface tumblehome and the inner port surface diverge from the centerline in approximately equivalent fashion.
The inner starboard surface and the inner port surface are each disposed: (i) vertically (i.e., in nontumblehome fashion); or, (ii) nonvertically, equivalently and oppositely angled upwardly away from the centerline (i.e., in nontumblehome fashion); or, (iii) nonvertically, equivalentsly and oppositely angled upwardly toward the centerline (i.e., in tumblehome fashion). According to some embodiments wherein the inner surfaces are tumblehome surfaces, the outer starboard tumblehome surface, the inner starboard tumblehome surface, the outer port tumblehome surface and the inner port tumblehome surface each define approximately the same tumblehome angle. Generally, according to inventive embodiments wherein the inner surfaces, as welt as the outer surfaces, are tumblehome surfaces, the outer starboard tumblehome surface, the starboard obliquely downfacing surface and the inner starboard tumblehome surface define, from an aft perspective, an approximate N-shaped starboard profile wherein the outer starboard tumblehome surface reaches a greater elevation than does the inner starboard tumblehome surface; the outer port tumblehome surface, the port obliquely downfacing surface and the inner port tumblehome surface define, from an aft perspective, an approximate reverse N-shaped port profile wherein the outer port tumblehome surface reaches a greater elevation than does the inner port tumblehome surface. Proceeding from the stern surface in a generally forward direction, the N-shaped starboard profile and the reverse N-shaped port profile each narrow in breadth in approximately equivalent fashion.
The present invention uniquely features a dual (both-sided) tumblehome, trimaran-like, integral hullform design. According to typical inventive embodiments, the inventive hullform includes a medial hull and two outrigger-analogue hulls which are integrally associated with the medial hull. According to typical inventive practice, there are no cross-structures for connecting the outrigger-analogue hulls to the medial hull; all three hulls are closely integrated into what is essentially a monohull hullform. According to many inventive embodiments, the inventive hullform is characterized by two tumblehome surfaces (one port, one starboard); one tumblehome surface is described by each outrigger-analogue hull, and two nontumblehome surfaces are described by the medial hull. According to other inventive embodiments, the inventive hullform is characterized by four tumblehome surfaces (two port, two starboard); two tumblehome surfaces are described by the medial hull, and one tumblehome surface is described by each outrigger-analogue hull.
The inventive dual tumblehome monohull hullform affords greater sea-keeping, stability and capacity (space or volume) vis-a-vis the conventional tumblehome monohull vessel, while also affording lesser structural weight vis-a-vis the conventional trimaran vessel. In comparison with conventional hulls, the inventive hull features a relatively moderate transom width; effectively in certain respects, the inventive hull""s transom width is the width of the transom at the rear of the inventive medial hull. Stability and seakeeping are furthered by the inventive vessel""s combination of the two lateral outrigger-analogue hulls and the medial hull characterized by a moderate transom width. The double (two-sided) tumblehome arrangement, on both sides of the inventive vessel, serves not only to reduce signatures but also to architecturally render, together with an upper portion of the medial hull, a kind of curtain over two mirror-image tunnels extending forward from the transom. The inventive hullform lends itself to application to a variety of types and sizes of vessels (ships, boats, etc.) and to association with a variety of types and sites of propulsion means. Depending on the inventive embodiment, the vessel""s topside can be xe2x80x9copenxe2x80x9d or xe2x80x9cclosed.xe2x80x9d
As compared with a conventional tumblehome monohull vessel, the tumblehome monohull vessel according to the present invention has superior characteristics, especially in terms of stability, internal volume and sea-keeping. The tumblehome monohull vessel according to the present invention also has superior characteristics as compared with a conventional trimaran vessel, especially in terms of structural weight. In terms of stability and sea-keeping, when the inventively configured vessel heels it advantageously acts to attain additional water plane area and additional righting force. In terms of internal volume, the inventively configured vessel inherently advantageously provides additional space by virtue of its structurally augmentative quality.